1625, 807 etc would do just fine are easy to find and cheap.
73 bill wa4lav
________________________________________
From: Amps [amps-bounces@contesting.com] on behalf of Roger (K8RI)
[k8ri@rogerhalstead.com]
Sent: Tuesday, February 17, 2015 9:13 PM
To: amps@contesting.com
Subject: Re: [Amps] Biasing a Class C modulated final
Not sure the 6L6 would be a good choice due to price, unless you have
some, or a good source. The price on them is astronomical. My guitar
amp uses 6 of them. I could purchase a nice, new amp for less than
replacing those tubes.
73
Roger (K8RI)
On 2/17/2015 5:14 PM, KA4INM wrote:
> On 02/17/2015 03:11 PM, Paul KW7Y Baldock wrote:
>
>> I am building a 2x813 class C final modulated by 2x813.
>
>> The typical way to bias the class C final is with a combination of fixed
>> bias applied to the control grid and bias derived from the rf drive
>> through a grid resistor.
>
>> Rather than fixed bias applied to the grid it seems that I could achieve
>> the same effect by using a pseudo zener in series with the cathode,
>> similar to what is used in cathode driven linears.
>
>> Any thoughts on this approach?
>
> I am guessing common cathode RF amplifier, a more standard way to do
> it would be an adjustable bias supply and a clamp tube on the screen
> grid. (6L6 or similar) look into any pre-1960 ARRL hand book.
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